JP5495647B2 - Wafer processing method - Google Patents

Description

  The present invention thins the wafer by fixing the front side of the wafer on which the plurality of devices are defined by the division lines formed in a lattice shape on the surface to the support member, and grinding or polishing the back side of the wafer The present invention relates to a wafer processing method.

  In the conventional method of thinning the wafer by grinding or polishing the back surface of the wafer in which a plurality of devices are partitioned by a predetermined division line formed in a lattice shape on the front surface, a protective adhesive tape is applied to the front surface side of the wafer. The protective adhesive tape side is brought into contact with the surface of the chuck table of the grinding device or the polishing device, the wafer is placed on the chuck table, and the back side is thinned by grinding or polishing with a grinding wheel or the like ( Patent Document 1). After that, the protective adhesive tape is removed from the thinned wafer surface and a dicing tape is attached to the back surface of the wafer, and then the wafer is placed on the chuck table of the cutting device via the dicing tape. And the wafer is divided into devices or chips.

JP 2006-303051 A

  For example, when the device on the front side is a micromachine device such as an acceleration sensor, if a protective adhesive tape is applied to the micromachine device side for grinding or polishing, the micromachine device may be damaged at the time of peeling. There is. Further, when the thickness is made very thin, for example, 50 μm or less, there is a problem in that the wafer itself is damaged when the protective adhesive tape is peeled off due to the extremely thin thickness.

The present invention has been made in view of the above circumstances, the principal object, without damaging the device surface of the wafer, and wafers breakage of the wafer even when the ultra-thin portable 及 manner It is to provide a new and improved wafer processing method that can be avoided.

According to the present invention, as a wafer processing method for achieving the main technical problem, the surface side of a wafer in which a plurality of devices are defined by division lines formed in a lattice shape on the surface is used as a support member. A wafer processing method for fixing and thinning the wafer by grinding or polishing the back surface of the wafer,
A recess forming step of forming recesses corresponding to the outer peripheral portion of the wafer on the surface of the support member that is the same size or larger than the wafer and open to the surface side and the outer peripheral surface side of the support member ;
After the recess forming step, the wafer is placed on the surface of the support member with the surface of the wafer being brought into contact with the surface of the support member and the outer edge of the wafer corresponding to the recess. And then bonding the wafer over the recess and the outer edge of the wafer, and fixing the wafer to the surface of the support member;
After the fixing step, a thinning step of thinning the wafer by grinding or polishing the back surface of the wafer fixed to the front surface of the support member;
A wafer processing method including a separation step of separating the support member and the wafer after the thinning step is provided.

Preferably, the adhesive has a property that the adhesive force is reduced by an external stimulus, and in the separation step, the support member and the wafer are separated by applying an external stimulus to the adhesive. It is. Further preferably, after the thinning step and before the separation step, a laser beam having a wavelength that is transmissive to the wafer is irradiated along the division line from the back side of the wafer. An altered layer forming step for forming an altered layer inside the wafer;
After the deteriorated layer forming step and before the separating step, an expanding tape attaching step of attaching an expanded tape to the back side of the wafer;
Preferably, after the separation step, the expansion tape is expanded to separate the wafer along the deteriorated layer into individual chips and to form a separation between the chips. .

  A wafer is placed on a support member having a concave portion corresponding to the outer peripheral portion where a wafer device is not formed, with the front side of the wafer in contact with the surface of the support member, and the concave portion and the outer peripheral edge of the wafer. In this way, the adhesive is loaded to the support member, thereby fixing the wafer to the support member, so that the adhesive does not adhere to the device on the wafer and the device is prevented from being damaged in the subsequent separation process. Is done. Moreover, the wafer after grinding or polishing can be separated from the support member with sufficient ease, and even when the wafer is made extremely thin, damage to the wafer can be avoided as much as possible.

The perspective view which shows a wafer. The flowchart which shows 1st embodiment of the processing method which concerns on this invention. Sectional drawing which shows a recessed part formation process. Sectional drawing which shows the adhering process. Sectional drawing which shows the adhering process. Sectional drawing which shows a thinning process. Sectional drawing which shows the isolation | separation process in 1st embodiment. The flowchart which shows 2nd embodiment of the processing method which concerns on this invention. Sectional drawing which shows a deteriorated layer formation process. Sectional drawing which shows an expand tape sticking process. Sectional drawing which shows the isolation | separation process in a 2nd implementation method. Sectional drawing which shows a division | segmentation process. Sectional drawing which shows a division | segmentation process.

  Hereinafter, preferred embodiments of the processing method of the present invention will be described in more detail with reference to the accompanying drawings.

  As shown in FIG. 1, the wafer 2 of this embodiment is composed of a silicon substrate 4, and a plurality of devices 8 are formed on the surface 6 side of the silicon substrate 4 by dividing lines L formed in a lattice shape. Each of the devices 8 is formed with a micromachine device.

  FIG. 2 shows a flow chart relating to the first embodiment of the processing method according to the present invention. First, the recess forming step S1 is performed. In the recess forming step S <b> 1, a support member 10 having the same dimensions as the wafer 2 or larger than the wafer 2 is prepared. In the present embodiment, the support member 10 is a glass substrate having the same dimensions as the wafer 2. As shown in FIG. 3, the support member 10 is formed with a recess 11 in the outer peripheral portion of the support member 10 by a known cutting device. The configuration of the cutting device itself may be a well-known form disclosed in, for example, Japanese Patent Application Laid-Open No. 2008-262983, and detailed description thereof is omitted in this specification. The support member 10 is sucked and held by the chuck table 12 of the cutting apparatus. The chuck table 12 is disposed so as to be rotatable about a central axis extending in the vertical direction.

  A cutting means 14 is disposed above the chuck table 12. The cutting means 14 includes a spindle 16 having a rotation axis extending in the Y-axis direction (horizontal direction in FIG. 3), which is a horizontal direction, and the spindle 16 is rotated at high speed by a motor (not shown). . A cutting blade 18 is attached to the tip of the spindle 16 via a blade mount 20 perpendicular to the rotational axis. As the cutting blade 18, a cutting blade having a blade thickness that is the same as or wider than the width of the recess 11 to be created is appropriately selected. The cutting means 14 is disposed so as to be movable in the Z-axis direction, which is a direction perpendicular to the holding surface of the chuck table 12, and is moved up and down in the Z-axis direction. The cutting means 14 is disposed so as to be movable in the Y-axis direction, which is a direction parallel to the holding surface of the chuck table 12.

  The support member 10 is sucked and held on the chuck table 12 of the cutting apparatus, and the rotation of the cutting blade 18 is started. The cutting means 14 is moved to position the cutting blade 18 on the outer peripheral edge of the support member 10. Next, the lower end of the cutting blade 18 descends to a predetermined position located slightly below the surface of the support member 10. Thereafter, with the cutting blade 18 positioned at the position, the chuck table 12 is rotated at 360 ° or more at a predetermined rotational speed. As a result, as shown in FIG. 3, a recess 11 is created in the outer peripheral edge of the support member 10 (recess forming step S1). As will be understood by referring to FIG. 4, the recess 11 is formed corresponding to the outer edge 22 of the wafer 2 to be fixed.

  After the recess forming step S <b> 1, the surface 2 of the wafer 2 is brought into contact with the surface 24 of the support member 10 and the outer edge 22 of the wafer 2 is made to correspond to the recess 11 of the support member 10. Place it on top (Figure 4). Next, the adhesive 26 is loaded across the concave portion 11 and the outer edge portion 22 of the wafer 2, and the wafer 2 is fixed to the surface 24 of the support member 10 (FIG. 5: fixing step S2). Since a high-viscosity adhesive 26 is selected and the adhesive 26 is loaded into the recess 11, the adhesive 26 does not enter between the surface 6 of the wafer 2 and the surface 24 of the support member 10. The adhesive 26 is preferably an adhesive whose adhesive strength is reduced by an external stimulus. In the present embodiment, the adhesive 26 is UV curable, which reduces the adhesive strength when irradiated with ultraviolet rays.

  After the fixing step S2, a thinning step S3 of the wafer 2 is performed. In the thinning step S3, the silicon substrate 4 of the wafer 2 is ground by a grinding device. As shown in FIG. 6, the back surface 28 of the support member 10 to which the wafer 2 is fixed is brought into contact with the chuck table 30 of the grinding device, and the support member 10 to which the wafer 2 is fixed is sucked and held on the chuck table 30. The chuck table 30 is disposed so as to be rotatable about a central axis extending in the vertical direction. The configuration of the grinding apparatus itself may be a known form disclosed in, for example, Japanese Patent Application Laid-Open No. 2000-354962, and detailed description thereof is omitted in this specification. The grinding apparatus includes a grinding tool 32 disposed to face the chuck table 30. The grinding tool 32 faces the holding surface of the chuck table 30. The grinding apparatus includes a motor (not shown) that rotates the grinding tool 32 and a grinding feed means (not shown) that feeds the grinding tool 32 vertically downward. The grinding tool 32 is formed of a disc-shaped grinding wheel base 34 and a plurality of arc-shaped grinding wheels 36 mounted on the lower surface of the grinding wheel base 34.

  The support member 10 with the wafer 2 fixed on the chuck table 30 is sucked and held, the rotation of the grinding tool 32 and the chuck table 30 is started, and the outer edge of the grinding tool 32 is positioned at a position covering the rotation center of the wafer 2. Then, the grinding tool 32 starts to descend at a predetermined grinding feed rate by the grinding feed means. As shown in FIG. 6, the silicon substrate 4 of the wafer 2 is thinned to a predetermined thickness by the grinding tool 32, and the grinding feed is stopped (thinning step S3). At this time, when thinning very thinly, for example, when thinning to 50 μm or less, the adhesive layer of the protective adhesive tape is obtained by pasting the protective adhesive tape which is a conventional method and performing thinning grinding. Variation in the thickness of the wafer 2 after grinding due to the variation in thickness. However, in the processing method of the present invention, since the surface 6 of the wafer 2 is fixed to the support member 10 without an adhesive layer or the like, the thickness variation of the wafer 2 after grinding does not occur, and the accuracy is high. Ultra-thinning of 50 μm or less can be performed. In the thinning step S3, not only grinding using the grinding tool 32, but also thinning treatment by polishing such as well-known wet polishing, dry polishing, and chemical polishing may be performed.

  A separation step S4 is performed after the thinning step S3. As illustrated in FIG. 7, ultraviolet rays are irradiated from the back surface side of the support member 10 toward the adhesive material 26. Since the support member 10 is formed of a glass substrate and is transparent, ultraviolet rays are transmitted, the adhesive 26 is cured, and the adhesive force is reduced. As a result, the support member 10 and the wafer 2 can be easily separated (separation step: S4). In the present embodiment, the adhesive 26 is used in which the adhesive strength of the adhesive is reduced by irradiating ultraviolet rays, but there are other adhesives whose adhesive strength is reduced by other external stimuli such as heat. It can be suitably used according to the type of device.

  Next, the second embodiment will be described. In the case where the wafer 2 is divided along the division line L after the thinning step S3 for thinning, the second embodiment can be applied. As shown in FIG. 8, a deteriorated layer forming step S5 is performed after the thinning step S3 of the first embodiment and before the separation step S4. The deteriorated layer forming step S5 is performed by a laser processing apparatus as shown in FIG. The back surface of the support member 10 to which the thinned wafer 2 is fixed is brought into contact with the surface of the chuck table 38 of the laser processing apparatus, and the support member 10 to which the wafer 2 is fixed is placed on the chuck table 38. The chuck table 38 is arranged to be movable in the X-axis direction (perpendicular to the paper surface in FIG. 9) and the Y-axis direction (left-right direction in FIG. 9) by a moving mechanism (not shown). A laser irradiator (a main body portion is not shown) having a laser irradiation head 40 is disposed above the chuck table 38. The laser irradiator includes a laser beam oscillator having a known structure, a repetition frequency setting means, and the like. The laser beam oscillated from the laser beam oscillator is a laser beam having a wavelength that is transmissive to the silicon substrate 4 of the wafer 2. The deteriorated layer 42 is formed by being condensed inside. The chuck table 38 is scanned and moved in the X-axis direction and the Y-axis direction, and the deteriorated layer 42 is formed inside the silicon substrate 4 along all the planned division lines L (modified layer forming step: S5).

  An expanded tape sticking step (S6) is performed after the deteriorated layer forming step S5 and before the separating step S4. In the expanding tape attaching step S6, the silicon substrate 4 side of the wafer 2 is attached to the expanding tape 44, and the outer peripheral portion of the expanding tape 44 is formed on an annular support frame 46 having an inner peripheral diameter larger than the outer edge of the wafer 2. Sticking (expanding tape sticking step: S6). In the second embodiment, the separation step S4 is performed thereafter. The silicon substrate 4 is adhered to the expanded tape 44, and the back surface 28 side of the support member 10 is exposed. As shown in FIG. 10, the adhesive 26 is irradiated with ultraviolet rays from the back surface 28 side. Since the support member 10 is formed of a glass substrate and is transparent, ultraviolet rays are transmitted, the adhesive 26 is cured, and the adhesive force is reduced. As a result, as shown in FIG. 11, the support member 10 can be easily detached from the wafer 2 (separation step: S4).

  Next, the dividing step S <b> 7 is performed by the tape expansion device 48 on the wafer 2 supported by the support frame 46 and the expanded tape 44. As shown in FIG. 12, the tape expansion device 48 includes a fixed cylinder 50, a plurality of holding means 52 arranged radially outward of the fixed cylinder 50, and a moving means 54 that moves the holding means 52 in the vertical direction. It consists of and. The holding means 52 includes a mounting table 51 a on which the support frame 46 is mounted and a clamp 51 b that is fixed to the mounting table 51 a and holds the support frame 46. The support frame 46 is mounted on the upper surface of the mounting table 51a and is gripped by the clamp 51b. At this time, the upper surface of the fixed cylinder 50 and the upper surface of the holding means 52 are held on substantially the same plane. Next, when the holding means 52 is moved downward by the moving means 54 in the direction of arrow A in FIG. 12, the holding means 52 descends with respect to the fixed cylinder 50 as shown in FIG. As a result, as shown in FIG. 13, the devices are divided along the altered layer 44 formed along the planned division line L, and the intervals between the devices are further expanded (division step: S7).

2 Wafer 4 Silicon substrate 8 Device (micromachine device)
10 Support member 11 Recess 12 Chuck table (cutting device)
18 Cutting blade 26 Adhesive 30 Chuck table (grinding equipment)
32 Grinding tool 38 Chuck table (Laser processing device)
40 Laser irradiation head 42 Altered layer 44 Expanded tape 48 Tape expansion device S1 Concave forming process S2 Adhering process S3 Thinning process S4 Separating process S5 Altered layer forming process S6 Expanding tape attaching process S7 Dividing process L Scheduled dividing line

Claims (3)

A wafer surface in which a plurality of devices are partitioned by a dividing line formed in a lattice on the front surface is fixed to a support member, and the back surface of the wafer is ground or polished to thin the wafer. A processing method,
A recess forming step of forming recesses corresponding to the outer peripheral portion of the wafer on the surface of the support member that is the same size or larger than the wafer and open to the surface side and the outer peripheral surface side of the support member ;
After the recess forming step, the wafer is placed on the surface of the support member with the surface of the wafer being brought into contact with the surface of the support member and the outer edge of the wafer corresponding to the recess. And then bonding the wafer over the recess and the outer edge of the wafer, and fixing the wafer to the surface of the support member;
After the fixing step, a thinning step of thinning the wafer by grinding or polishing the back surface of the wafer fixed to the front surface of the support member;
A wafer processing method including a separation step of separating the support member and the wafer after the thinning step.   2. The wafer according to claim 1, wherein the adhesive has a property in which an adhesive force is reduced by an external stimulus, and in the separation step, the support member and the wafer are separated by applying an external stimulus to the adhesive. Processing method. After the thinning step and before the separation step, a laser beam having a wavelength that is transmissive to the wafer is irradiated along the division line from the back side of the wafer to the inside of the wafer. An altered layer forming step for forming an altered layer;
After the deteriorated layer forming step and before the separating step, an expanding tape attaching step of attaching an expanded tape to the back side of the wafer;
The separation step includes expanding the expanded tape to separate the wafer along the deteriorated layer into individual devices and forming a space between the devices after the separating step. The processing method of the wafer as described.

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